Boring with Sherline lathe

[BiggerNoise]

I need to create a 14.5mm (~.591) hole in the end of some aluminum.

I have a drill that's a bit less than 1/2" with a reduced shank that I can get into the chuck of my lathe and make a hole.

I don't have a bigger drill and wouldn't think that one would necessarily help; at a certain point my little lathe is going to run out of oomph. So, I'm expecting to finish the hole by boring it.

I bought a basic 1/4" HSS tool set from Amazon which has a boring tool, but it's too large to fit into the hole that my largest drill can make. It appears that the Sherline boring tools will work with the hole that I have, but the few references to them I have seen in this forum are not very positive.

To be fair, those references were in the context of the milling machine not the lathe, so they may be OK for my purposes.

Ultimately, I'd like to reach the point where I can grind my own tools, but I'm very new to machining and am trying to concentrate on specific skills. Is there a boring tool that works with the Sherline lathe that folks would be comfortable recommending?

 

[mmcmdl]

You just need a smaller diameter boring bar . Nothing special about it .

 

[sj.ccim]

I've used the Sherline boring tool in the tool post on aluminum a number of times. I've never had any problems. I just drill a pilot hole to desired depth large enough in diameter for boring tool clearance and take my time with light cuts. Keep the tool sharp.

 

[BiggerNoise]

I've used the Sherline boring tool in the tool post on aluminum a number of times. I've never had any problems. I just drill a pilot hole to desired depth large enough in diameter for boring tool clearance and take my time with light cuts. Keep the tool sharp.

Thanks, I'll pick one up

 

[mikey]

How deep is your bore? That is really what you need to know because the deeper the bore is, the bigger the boring bar must be in order to hold its accuracy. You are looking for the largest bar you can fit in the hole and still clear coiled chips easily. Note that a steel (HSS, cobalt) can extend about 4 times its diameter beyond the boring bar holder before you begin to have inconsistencies in accuracy. A carbide bar can go 8-10 times its diameter before running into this same problem.

The Sherline tools are HSS. The 5/16" bar in 1.5" length, can theoretically go 1.25" deep so if your bore is less than this, you're good. A Micro 100 solid carbide bar of the same diameter would be able to about 2.5" deep.

If I had to bore that hole, I would use a 1/4" to 5/16" inserted carbide bar but I also have cobalt and solid carbide bars to do the same thing, depending on the depth.

So, how deep is the bore?

 

[BiggerNoise]

1 inch should do it. I'm going to thread an aluminum foot peg over a steel rod that will fasten to the motorcycle. We might end up wanting to go a bit deeper, but I don't think I can get the pilot hole much deeper than 1.5".

The steel post has a diameter perfect for an M16 thread, so that's what I'll end up cutting on the post and inside the bore.

So, not having a real great feel for how much thread connection is really required, let's use 1.25 as the depth of the bore.

 

[mikey]

Why can't you get the pilot hole deeper than 1.5"? Just drill it to the depth you need and bore it to the size you need. Of course, as you go deeper, you will need a larger boring bar.

At 1.25" depth, that 5/16" bar from Sherline will work for a 16mm hole (less for threading). However, you can also go with a Micro 100 solid carbide bar like this one for nearly the same cost and it will go 2" and hold tight tolerances. They are easy to sharpen and will last decades if you don't crash it. These bars are amongst the finest solid bars made and I would go with this one before one from Sherline.

Max strength of a fastener should be achieved at about 1.5 times the diameter so thread it at least that deep. For a 16mm hole, about 1" of thread should work okay.

 

[BiggerNoise]

The combination of the length of the drill and the length of the part was making me nervous once I got in there. It's been a couple weeks since I was playing with this, but IIRC, I was having to start the lathe with the drill in the part. Let's chalk that one up to not really knowing what I am doing and assume that I can drill as deep as my drill.

Do I need to get the round holder from sherline to mount that Micro 100 bar? I have 3/8" holders that work with square tools, not sure if there's enough flat on that bar to grip.

Certainly appreciate the helpful advice, hope to be able to pay it forward some day.

 

[mikey]

Don't worry, you can start the lathe with the drill buried in the part. The stroke of the Sherline ram is so short that we have to do that to go deep sometimes.

I think the flats on the Micro 100 bar will hold it steady enough in your tool holder but I'm not entirely sure. You'll have to try it and see how it works. Make sure the inner edge of the bar is up against the wall of the holder and tighten the screws evenly and firmly. At some point, when you have a mill running, you need to make a boring bar holder for your lathe. You can see an example of the post I made for my Sherline in this article.

You are going to find that the Sherline lathe can bore really, really accurate holes. I've been using this lathe for a long time and I'm still amazed at how accurate it is. Of course, the lathe got more accurate as the user gained experience so there is that.

 

[BiggerNoise]

Oh my goodness, I think a part of my head just exploded .

I'll try that boring bar you linked to. I've been reluctant to try the mill b/c I'm afraid I'm going to go nuts buying extra toys to go on it. With the lathe, I'm pretty close to having all the bits and pieces that I need and just needing to get better at the operations.